This invention relates to computer monitoring devices and more specifically to a diagnostic device for determining the thoroughness of software and firmware tests. To determine if a computer is operating up to expectations, one or more software test programs are run on the machine and the results are compared against standard results. Any deviations would indicate a malfunction in the machine under test. The problem associated with such testing is that the software test programs may not be testing one or more features of the machine and if such is the case, a malfunction in the untested feature would go undetected and uncorrected. A non-test program which uses the defective feature would, of course, cause an error to appear in the computer's output. It is, therefore, desirable to have the means whereby a quantitative measurement can be made of the scope of coverage of the test program so that gaps in the testing can be filled.
A patent of interest for its teaching of monitoring the operation of a computer for the purpose of detecting sources of malfunctions is U.S. Pat. No. 3,771,131, entitled, "Operating Condition Monitoring in Digital Computers", by A. T. Ling. In this patent, there are provided hard-wired connections to test points located within the computer under test. A switching arrangement selects a particular plurality of these test points, as a set, and during preselected operational phases, the signals developed at the selected test points are entered into a register. This operation has been called a "snapshot". The signal pattern developed at a particular snapshot is then compared against known snapshots with any difference indicating a malfunction. Snapshots may be compared by visually displaying the snapshot on a CRT and having an operator with an appropriate chart, or the like, noting any differences. Alternatively, there is suggested comparing the snapshots stored in the register with known snapshots stored in corresponding preprogrammed registers such that a difference would cause a warning indicator to be activated. Devices similar to the one disclosed in the referenced patent are effective in determining malfunctions, but it is first assumed that the device checks all potentially defective circuits, which may, in fact, not be the case. The present invention is directed to a computer address analyzer which determines the quality of testing by indicating which portions of a computer system have not received adequate testing.